1. Field of the Invention
This invention relates to a device for selecting a desired voltage, and particularly to a variable resistor provided with a seesaw-like operating piece.
2. Description of the Prior Art
It has become common that a zoom lens is incorporated in a television or motion picture camera, and zooming adjustment is accomplished manually or electrically. In the case of electrical zooming, it is necessary to effect designation of the zooming direction, i.e., whether the angle of view is to be rendered wide or telephoto, and designation of the zooming speed. For this reason, a seesaw switch is usually used. In particular the zooming direction is determined by which end edge of the switch seesaw piece is pushed and the zooming speed is determined by the amount of the push-in of the piece. The zoom ring of the lens barrel is connected to a motor which is controlled by the output of a potentiometer (a variable resistor regulated by rotating its shaft) which in turn is regulated by the seesaw switch. The conventional seesaw switch is provided with a seesaw piece rockable relative to a rotary shaft and a spring for maintaining the seesaw piece neutral. Further, a semigear meshing with a gear for rotating the shaft of the potentiometer is formed in a portion of the seesaw piece. Accordingly, when one end of the seesaw piece is pushed in, the semigear causes the shaft of the potentiometer to be rotated through the association of the semigear and the gear.
Back-lash occurs to the gear train and therefore, the movement of the seesaw piece does not smoothly correspond to the movement of the potentiometer. As a result, accurate control becomes impossible and the effect during operation is bad. While, on the other hand, the adjustment for alleviating the back-lash during the assembly step requires time and labor.